Add mechanism to wake native loop

[kevinresol]

Two changes so Haxe EventLoop works correctly with a blocking native loop (e.g. libuv UV_RUN_ONCE on HashLink):

1. nativeLoop.run(maxBlock) — pass the next Haxe event deadline into the native loop so a blocked poll returns when a Haxe timer is due, even if no I/O is ready.
2. nativeLoop.wake() — cross-thread enqueue calls this (via EventLoop.wakeup()) so another thread posting work can unblock a poll that would otherwise wait indefinitely.

Together these replace the previous HL busy-spin on UV_RUN_NOWAIT with a proper sleep/wake model: the OS poller blocks when idle, and wakes for either native I/O, a Haxe deadline, or a cross-thread task.

Pair with HaxeFoundation/hashlink#958